An all-too-common example of this is the Vietnam war, which may have been entered simply because, after the McCarthy Witch Hunt, no politicians were brave enough to avoid publically condemning communism for communism's sake: "As a consequence of McCarthyism, no U.S. politician [was] willing to appear to be 'soft' on Communism." Going to war was a reactionary measure, and by the time a concrete goal was formulated, it was: how can we get out without losing face?

Perhaps the most complicated precept of Just War Theory is that the war should do more good than harm. The difficulties lie in the definition of good and harm, as obviously the definitions of the two parties at war are at odds, or there would not be a war. During the American Civil War, the North was obviously convinced that slavery was an abomination and should be halted, and the South was just as obviously convinced that slavery was a perfectly moral trade, and the North's poorly-treated factory workers made them not only wrong, but hypocritical. Six-hundred thousand Americans died, both slave and free. Was more harm done, or was more good done? The victors would clearly make the claim that more good was done,...

All possibilities for diplomacy must be completely exhausted before war is a viable option. In the first world war, over eight million people died, and the effects of attempted genocide still haunt an entire race years later. War has awful consequences, and a failure to pursue other means of resolution is simply irresponsible.
Historically, conventions of warfare are defined by just ad bellum -- when is it right to go to war?, jus in bello -- rules of engagement, and jus post bello -- how should a war end, and how should victors act?

These definitions allow enemies to define the rules of their Just War.

The difficulty with forming a "Just War" is that there is no person capable of applying all five criteria to forming said conventions. While a number of paradoxes could be identified in the criteria, the primary area of subjectivity is the definition of harm vs. good. A popular saying states, "to the victors go the spoils." Part of those spoils is the ability to write history.

The result, as is certainly demonstrated by the United States, is that all country's consider their own instigated wars justified, with the exception of a very few (such as the Vietnam war), while most other countries consider that same war in gross violation of the precepts of the just war.

Just War Theory. Article online. Available at http://www.justwartheory.com.

Moseley, Alexander. Just War Theory. Martin, TN: University of Tennessee in Martin, 2006. Article online. Available at http://www.iep.utm.edu/j/justwar.htm.

The Gulf War: Kawait. Article online. Available at http://www.indepthinfo.com/iraq/kuwait.shtml.

The Vietnam War. Article online. Available at http://www.historyplace.com/unitedstates/vietnam/index-1945.html.

The Civil War. Article online. Available at http://www.civilwar.com.

Wilde, Robert. Overview: The First World War. Article online. Available at http://europeanhistory.about.com/od/worldwar1/a/ovww1.htm.